The present invention relates to plugs for closing openings in conduits and more particularly to plugs for obturating lift holes or apertures through the wall of concrete drain pipes and the like.
Poured cement or concrete conduits, such as drain pipes, which provide a passageway for a liquid fluid such as water which is normally not under pressure, and large conduits for the passage of utility cables, telephone cables or the like are sometimes provided with a through-wall opening, or "lift-hole", disposed laterally substantially aligned with the center of gravity of the conduit. The lift hole greatly facilitates the installation of the conduit in a trench, for example, by means of an appropriate lifting arrangement passed through the lift hole and attached to the end of a crane cable or sling. By means of such an arrangement, the conduit is conveniently loaded on flat bed trucks, semi-trailers, or railroad cars, unloaded at a work site and positioned in a trench or excavation, several lengths of conduit being placed end to end such as to form a continuous conduit for drain water or the like, or for utility and telephone cables.
Prior to filling the trench with earth the lift holes are covered with a brick, a piece of concrete, a sheet of metal, or any other convenient means, and a shovelful of concrete is poured over the lift hole covering. After the concrete has set, the trench is filled, and the lift hole covering prevents earth from penetrating within the conduit through the lift hole.